1. Field of the Invention
The present invention relates to a field emission type cold cathode structure (spindt type cathode structure) and an electron gun having the cathode, in particular to a field emission type cold cathode structure and an electron gun using the cold cathode which is capable of preventing electron emission error due to impurities etc. infiltrated into the cathode part.
2. Description of the Prior Art
FIG. 1 illustrates a structure of a standard CRT (Cathode Ray Tube) in accordance with the prior art.
As depicted in FIG. 1, the standard CRT (Cathode Ray Tube) comprises a glass container 1, an electron gun 2, an electron beam 3, a deflection yoke 4, and a fluorescent screen 5, and it will now be described as below.
First, the electron gun 2 is installed at the end of the vacuum glass container 1, the electron beam 3 generated from the electron gun 2 is deviated by the deflection yoke 4 generating a magnetic field, and the electron beam is emitted to the fluorescent screen 5, accordingly the fluorescent screen 5 emits by being excited by the collision with the electron beam 3.
And, when the described CRT (Cathode Ray Tube) is actually used, a certain image can be displayed by controlling the quantity of the electron beam in accordance with an input image signal, deviating the electron beam 3 two-dimensionally, and scanning it on the fluorescent screen 5.
FIG. 2 illustrates a structure of a cathode used in an electron gun of a CRT in accordance with the prior art.
As depicted in FIG. 2, it comprises a nickel cylinder 6, an emitter 7, a heater 8, and a steatite disk 9. It will now be described.
First, the emitter 7 is installed at the front end of the nickel cylinder 6, herein an oxide cathode constructed with Ba, Ca, Sr etc. is widely used.
In addition, a cathode of high electric current density fabricated by impregnating an emitter into a porous tungsten can be used also.
In addition, the heater 8 is installed inside of the nickel cylinder 6, the electron beam is emitted from the emitter 7 to the vacuum. The cathode is mounted on the steatite disk 9 in order to make the assembly of the electron gun easier.
FIG. 3 illustrates a structure of a section of the electron gun used in the CRT in accordance with the prior art.
As depicted in FIG. 3, it comprises a first control electrode 10, a second control electrode 11, a third control electrode 12, a fourth control electrode 13, a free focus electron lens 14, a main electron lens 15, and a crossover of an electron beam 16, it will now be described as below.
First, the first control electrode 10 and second control electrode 11 for controlling the electron beam are installed on the front of the emitter 7 installed on the cathode.
In addition, the third control electrode 12 and fourth control electrode 13 are placed in order to form the main electron lens 15 for making the electron beam 3 into a detailed spot beam on the fluorescent screen 5.
In addition, the free focus electron lens 14 of the electron beam 3 is formed by the second control electrode 11 and third control electrode 12.
Direction dependency of the electron beam density emitted from the cathode, namely, electric current density j(xcex8) emitted from a normal line to a xcex8 direction about current density j(A/m2 steradian) vertical direction to the fluorescent screen, can be described as below Equation 1.
j(xcex8)=j cos xcex8
Herein, the j describes the current density vertical to the fluorescent screen.
In addition, the emitted electron is discharged with a certain statistical initial velocity distribution, xe2x80x98distribution of mark cellxe2x80x99 about the velocity distribution of gas molecules can be adapted to a temperature corresponding to a temperature of the cathode.
As described above, in order to focus the electron emitted from each point of the cathode on one point of the fluorescent screen, various structures are provided for a control electrode for forming the main electron lens 15 and a control electrode for guiding the electron beam to the main electron lens.
FIG. 4 illustrates a field emission type cold cathode structure in accordance with the prior art.
As depicted in FIG. 4, it comprises a substrate glass 101, a base electrode 102, an insulating layer 103, a gate electrode 104, an emitter chip, e.g. emitter tip, 105, and an electron beam 106, a power 107. It can be described as below.
First, the emitter chip 105 constructed with a very small electric conductor (for example, molybdenum) having a cone shape is formed on the base electrode 102 formed on the substrate glass 101.
The gate electrode 104 constructed with an electric conductor (for example, nickel) is formed on the front end of the emitter chip 105 so as to surround the emitter chip 105.
And, the insulating layer 103 (for example, sio2) is placed between the base electrode 102 and electrode 104 in order to insulate them.
As described above, when a certain voltage Vg is applied from the power 107 between the base electrode 102 and gate electrode 104, very strong field occurs on the front end of the emitter chip 105, and electron (electron beam 106) is emitted from the front end of the emitter chip 105.
When the electron is emitted from the front end of the emitter chip 105, the electron beam current as about 350 xcexcA per 1 spot is required on the fluorescent screen, it is impossible to get the required electron beam current on the fluorescent screen with the one emitter chip 105.
Accordingly, in order to get the required electron beam current, the cathode is constructed by forming the plurality of emitter chips 105 on the two dimensional plane.
FIG. 5 illustrates a section of a field emission type cathode structure including the plurality of emitter chips in accordance with the prior art, herein a reference numeral 51 describes impurities.
As depicted in FIG. 5, when the impurities having the conductivity are stuck to the emitter chip 105 by a certain cause, the base electrode 102 and gate electrode 104 are in short circuit states.
When the base electrode 102 and gate electrode 104 are in the short circuit states, at this time high current flows between the base electrode 102 and gate electrode 104 through the emitter chip 105 and impurities 51. According to this, the voltage can not be applied between the emitter chip 105 and gate electrode 104, therefore the electron is not emitted from the other emitter chip 105.
In the prior art, there is the number of parts increase problem in the control electrode structure.
In addition, in the structure of the cathode in accordance with the prior art, because the electron is emitted by a heating method, although a main power of a television set is ON, a picture having good picture quality is not displayed on the CRT of the television set until the temperature of Ba reaches to the electron emission temperature.
In addition, in the CRT used for the general television, the required electron beam current is about 350 xcexcA per one spot of the fluorescent screen, however the power for heating the cathode is required about 2 W, accordingly the electron emission efficiency is low.
In addition, in the prior art, when Ba as the electron emission material is used for a long time, it evaporates slowly by being heated, accordingly the electron emission efficiency deteriorates slowly.
In addition, in the prior art, because the electron emitted from the cathode surface is radiated from each point to each region and the initial velocity is irregular, in order to get the detailed electron beam spot on the fluorescent screen, the lots of control electrodes are required.
In addition, in the prior art, when the electron is emitted from the front end of the emitter chip 105, because the electron beam current as about 350 xcexcA per one spot on the fluorescent screen is required, it is impossible to get the required electron beam current on the fluorescent screen with the one emitter chip 105.
In addition, in the prior art, when the base electrode 102 and gate electrode 104 are in the short circuit states, at this time high current flows between the base electrode 102 and gate electrode 104 through the emitter chip 105 and impurities 51. According to this, the voltage is not applied between the emitter chip 105 and gate electrode 104, therefore the electron is not emitted from the other emitter chip 105.
Accordingly, the object of the present invention is to provide a field emission type cold cathode structure which is capable of preventing electron emission error due to impurities etc. by constructing a field emission type cold cathode structure emitting electron by the field without using a structure emitting electron by heating.
The other object of the present invention is to provide a field emission type cold cathode structure which is capable of expanding its life span semi-permanently, improving the electron emission efficiency, reducing power consumption, and simplifying its structure.
The another object of the present invention is to provide an electron gun using the field emission type cold cathode structure in accordance with the present invention.
In order to achieve the objects of the present invention, the field emission type cold cathode structure in accordance with the present invention having a plurality of emitter chips formed on a base electrode, a gate electrode formed on a circumference of the each emitter chip, an insulating layer placed between the base electrode and gate electrode in order to insulate them, a certain DC (Direct Current) voltage applied between the base electrode and gate electrode comprises a fusible metal layer formed between the base electrode and the each emitter chip.
In the field emission type cold cathode structure, a focus electrode is installed on the upper portion of the gate electrode with an insulating layer between them.
In the field emission type cold cathode structure, the focus electrode is installed on the upper portion of the gate electrode with the insulating layer between them, and a control electrode is installed on the upper portion of the focus electrode with an insulating layer between them.
In addition, the field emission type cold cathode structure having the plurality of emitter chips formed on the base electrode with a certain interval, the gate electrode formed on a circumference of the each emitter chip, the insulating layer between the base electrode and gate electrode comprises gate electrodes formed on a circumference of the each emitter chip, main electrodes installed on the outer circumference surrounding the gate electrodes, and fusible metal layers formed between the main electrodes and gate electrodes.
In the field emission type cold cathode structure, a certain voltage is applied between the base electrode and main electrode.
In addition, in the electron gun using the field emission type cold cathode structure having a cathode part, a main electron lens, a first and a second focus electrodes, the cathode part comprises a plurality of emitter chips formed on the base electrode with a certain interval, a gate electrode formed on a circumference of the each emitter chip, a fusible metal layer formed between the base electrode and each emitter chip, a focus electrode formed on the upper portion of the gate electrode through the insulating layer, and a first and second focus electrodes formed on the front of the control electrode.
In the electron gun using the field emission type cold cathode structure, the base electrode and gate electrode are insulated each other through the insulating layer.
In the electron gun using the field emission type cold cathode structure, the electron beam emitted from the plurality of emitter chips is focused on the main electron lens formed by the first and second focus electrodes without forming crossover.